Determination of the charge carrier compensation mechanism in Te-doped GaAs by scanning tunneling microscopy

Abstract

We identified the charge carrier compensation mechanism in Te-doped GaAs with atomically resolved scanning tunneling microscopy. Three types of defects were found: tellurium donors (TeAs), Ga vacancies (VGa), and Ga vacancy–donor complexes (VGa–TeAs). We show quantitatively that the compensation in Te-doped bulk GaAs is exclusively caused by vacancy–donor complexes in contrast to Si-doped GaAs. This is explained with the Fermi-level effect as the universal mechanism leading to Ga vacancy formation in n-doped GaAs, and a Coulomb interaction leading to the formation of the complexes. The quantification of the carrier compensation yields a −3e charge state of VGa in bulk GaAs.

Probing nanoscale potential modulation by defect-induced gap states on GaAs(110) with light-modulated scanning tunneling spectroscopy

“…Since the development of scanning tunneling microscopy ͑STM͒, various techniques based on STM have been employed to analyze the atomic structures and electronic states of defects and impurities on semiconductor surfaces. [2][3][4][5][6][7][8] Defects in semiconductors are electrically charged in general and affect the electronic properties of semiconductors through, for example, the Fermi level pinning and compensation of dopants. 3,4 Therefore, considerable efforts have been focused on determining the charge states of various types of defects by using STM.…”

“…[2][3][4][5][6][7][8] Defects in semiconductors are electrically charged in general and affect the electronic properties of semiconductors through, for example, the Fermi level pinning and compensation of dopants. 3,4 Therefore, considerable efforts have been focused on determining the charge states of various types of defects by using STM. 5,6 The sign of the electronic charge of a defect can be deduced from the topographic contrast of a STM image, which depends on the relationship between the charge of the defect and the polarity of the tunneling bias voltage.…”

“…Therefore, indirect methods, such as measuring the average distance between defects that reflect Coulomb repulsion and measuring the number of charged defects that are coupled with the predetermined dopants, have been employed in pioneering works to determine the charge states of defects. [3][4][5][6] For further advancement in functional materials and devices based on nanoscale science and technology, development of a method that enables the direct characterization of the surveyed individual defects is required.…”

Review—Dopant Selection Considerations and Equilibrium Thermal Processing Limits for n+-In0.53Ga0.47As

“…Quantum well intermixing studies of AlGaAs/GaAs heterostructure also indicate that diffusion of species which occupy the group III sublattice is enhanced by the introduction of n-type group IV and group VI dopants. 81,[95][96][97][98] Direct evidence of vacancies using STM have been confirmed in n-type GaAs [99][100][101] and positron annihilation results 102-109 also indicate that n-type doping results in higher concentration of vacancies than is observed in un-doped or p-type GaAs. There are also reports of superdilation of GaAs and InAs with n-type doping and dopant-vacancy complexes have been suggested as the cause for the unexpected increases in lattice parameter at high doping concentrations.…”

Local Structure Around Te in Heavily Doped GaAs:Te using X-Ray Absorption Fine Structure

“…Fuller and Wolfstirn [1] suggested creation of impurity molecules which trap electrons. Some papers indicate gallium vacancy associated with the Te As quasisubstitutional defect as responsible for the observed compensation eect [2,5,6]. This complex was suggested on the grounds of Moessbauer experiments [5], scanning tunnelling microscopy [6], and other techniques.…”